adding a basemen

huangyhg

adding a basement
the home that we currentlylive in is almost perfect.  the only thing it lacks is a basement.  the crawlspace is currently excavated 3-4' under the house.  i am considering adding a basement under the house.  what should i be concerned about in such a project?  thanks in advance for your comments.
1.  soils conditions
2.  getting waterproofing on your walls
3.  hiring a contractor that has proven experience in this type of project.
dnice-  what you want to do is feasible, but will probably be relatively expensive.  a structural engineer's services will definitely be required. as sperling said, you will also need to find a builder who is capable of doing it.  adding the basement space is not a small project. i suggest very carefully looking at what its going to cost before going further.  the value of your property can increase by adding the basement space, but that added value probably will not even come close to covering  engineering and construction costs.   
thanks for the responses.  we have been debating adding the basement or just purchasing or building a new house to get the added space.
i'd be concerned about the cost!  over the years, i've had many home owners ask about adding a basement.  none ever have.  you could underpin the house with concrete pit underpinning and then dig out the basement, or you could build a new basement away from the existing house and then have the house moved to the new basement by a house moving company.  both options are expensive.
i've seen it done a number of times....can be quite feasible.  the house is supported (or moved)on steel beams temporarily while the basement is formed and cast.
if you are in a good neighbourhood with prices going up, the cost can be worth it due to the increase in value of the house.
note that if you are going that far, you might consider an addition/renovation to the house such that you maximize the increase in value of the home (note that this depends on the value of the land, neighbourhood etc.).
reijo